[boost] Boost Threads Condition may block forever on clock change

Hello, I've noticed a strange change in behaviour when condition is called with xtime parameter, condition::timed_wait. If right after the condition is called the clock is moved back the code never exits from condition unless signalled, even moving the clock back forward did not seem to fix the problem. The test was done on Windows XP. Is this desired behaviour or a bug? It seems strange that the condition is based on the current time and not just on a time offset. Any help with resolving this would be really appreciated. Thank you, Alex